Externally fired perforating gun



Dec.` 23, 1947. P, w, MARTIN 2,433,231

` EXTEINALLY FIRED PERFQRATING GUN Filed oct. 29; 1945 '8 le lo lo l '/40 y l ls 27 --ls 52 42 i 1-111-", 14,11. '1'1"'. 'il'..l va." rr..

PatentedvDec. 23, 1.947y i UNITED sTA'rEs PATENT oEElcE 2,433,231 v EXTERNALLY FIRED PERFORMING GUN Philip w. Martin, Huntlngmn Park, Calif. Application october 29, 1945, serial No. 625,171

v A 12 Claims:

This invention relates to well perforating guns whereby projectiles are shot through the wall of casing set in a well to provide communica- 4tion of the interior of the casing with the surrounding formation. y

Guns of this character have been successfully and extensively employed. However, certain difculties have been encountered in the use of these guns, one diiiiculty resulting from. the necessarily short gun barrel length. In view of the shortness of the gun barrel, the propelling effect of the expanding gases from the burning of the powder charge in these guns is limited to .that short space of 'time which ittakes for the projectile to travel through the barrel. For the purpose of obtaining a greater utilization of the potential projectile-propelling capacity of the powder charge employed in these guns, many expedients have been adopted, among which are shear rings on the projectiles and plates or 20 ianges at the rear ends of the projectiles, to rei strain the projectiles from movement until the pressureof combustion products from the burning of the powder against the rear ends ,of the projectiles builds up to an Velective value. These expediente have accomplished higher projectile velocities and therefore greater penetrating abil-v ity of the projectiles but from tests and observations, I' have determined that an eiiicient use of the powder is not obtained in these guns and that too large a portion ofthe powder is expelled from the gun barrels in unburned state and therefore without useful effect.

It is. an object of my present invention -to greatly increase the projectile-propelling eniciency of the powder charge in perforating guns, as compared to that which is obtained in the `most ecient guns of this character'now employed. By use of the invention I am able to obtain from al given powder charge an increase of approximately 100% in 'the penetrating capacity of theprojectile, as the result of a great Y increase in velocity, or the same penetration by the piojectile with only approximately one-half the previously required powder charge. For example, in the practice of my invention, with seventy grains of powder I have produced greater penetration than is obtained by the use of one hundred and thirty grains of powder in theold type of gun having a shear plate at the rear end 'of the projectile.

It is an object of the invention toA provide in a periforatingl gun of the characteridescribed a propelling charge comprising a mass of powder grains and an eiective quantity of gaseous medium (including air) -in the propelling charge chamber, at least a portion of which gaseous medium occupies the spaces existing between the powder grains of the powder mass, and to provide a simple and effective means for exploding the powder charge by compression ofthe entire content of the propelling charge chamber which lies behind the projectile at the rear end of the gun barrel. It is an object of the invention, hereinafter described in detail as an example only, to provide a projectile firing arrangement wherein a r'lng charge of powderis placed in l the outer part of the gun barrel adjacent the front end of the projectile and the outer end of the gun barrel is closed by a wall which prevents the compression of the ring and propelling charges by hydrostatic pressure encountered in the well, and means are provided for igniting the ringcharge so that the pressure developed thereby will drive the projectile rearwardly in the gun b'arrelagainst the contents' of the propelling charge chamber, which contents include the powder charge and the gaseous elements residing in the propelling charge chamber, and which gaseous elements are distributed through- E out the small spaces existing between the powder grains of the propelling charge. The interspersed gaseous elements of the propelling charge are thereby compressed in an instantaneous manner, causing a rapid rise in the temperature throughout the entire propelling charge to or above the ignition point of the powder grains I ,through the gun barrel, so that the individual powder grains will have a burning time sutuciently long to produce a continued generation of gas to maintain pressure throughout the outward movement of the projectile through the relatively short gun barrel so that a high velocity thereof is developed. A further contribution to the emciency of the perforating gun is the closer approachV to complete burning of the powder grains, without detonation or rapid burning which approaches close to detonation, by the time the projectile leaves the gun barrel.

It is a further object of the invention to provide a simple `and effective means for ring the gun and for preventing application of pressure to powder charges in a gun of the character described, resulting from the lowering of the gun deep into the uid in a well in which the'perlforating operation is to be conducted. Accordingly, the desired ignition and` burning characteristies of the powder chargesare maintained,l 60 the result being that 'the operating characteristics of the gun are maintained substantially constant. regardlessly of the different hydrostatic pressures to which the gun is subjected ln the well.

A further object of the invention is to provide a perforating gun having the general characteristics referred to in the foregoing, wherein the loading operations are simplified and the manner of tiring the propelling charges is simple and eilective.

An object of the invention is to provide a Perforating'gun having a body with a plurality of gun bores, the inner end of each gun bore having therein a loosely dispersed firing charge containing a gas space or spaces. and means for preventing external pressure froml compressing the powder charge when the gun is lowered into a well, such means consisting of a thin'shell which entirely covers the outer ends of the bores and is maintained in sealing relation to the body.

It is a further object of the invention to provide a perforating gun wherein the propelling charges are exploded by compression resulting from inward movement of the projectile, this gun having a shell disposed around the gun body in such relation as to provide a space communicating with the outer ends of the gun barrels, and means for producing a fluid pressure in this space to drive the projectile rearward to compress the propelling charges. It is a further object to provide a gun of the character set forth in the preceding paragraph, wherein the pressure in the space between the body and the shell is produced by explosion of a firing charge in a chamber which communicates with the space.

Further objects and advantages of the invention will be brought out in the following part of the specification.

Referring to the drawing which is for illustrative purposes only,

Fig. 1 is a partly sectioned view of one embodiment of the perforating gun.

Fig. 2 is an enlarged fragmentary section taken as indicated by the line 2-2 of Fig. 1.

Fig. 3 is an enlarged fragmentary section showing an alternative means for producing pressure at the outer ends of the gun bores.

Fig. 4 is also a fragmentary section showing another means for producing pressure at the outer ends of the gun bores.

The perforating gun shown in Fig. 1 includes a metal body I having at its upper end a cable connection II by which an electric cable I2 is connected to the body I0, this cable I2 having an.

insulated conductor I3 extended therethrough for connection with the firing means I4 which is situated at the lower end of the internal body I5 of the cable connection II. In the body IIJ, at the lower end of the internal body I5 of the cable connection II, there is a firing charge chamber I6, communicating with the exterior of the gun body through a passage I'I.

The gun body I0 has a plurality of radial gun bores I8 which may be disposed along a spiral path. Around the exterior of the gun body I2 I place a shell or cover I9 which extends over and covers the outer ends of the gun bores I8. The shell I9 is disposed in sealing relation to the body I0. To accomplish this disposition of the shell I9, I have provided at the upper end of the body I0 an annular projection 20, which may be undercut so as to receive a, packing ring 2I which is pressuraliy engaged by the upper end of the shell I9. On the lower end of the body I0 there is a cap 22 having a counterbored cylindric wall 23 which V overlaps the lower end of the shell I9 and provides a space to receive an annular packing member 24. A nut 25 threaded onto ascrew 28 which projects downwardly from the body is employed to apply upward pressure against the cap 22 so that the packing member 24 will be compressed and the, shell I9 will be forced upwardly so as to compress the packing ring 2|.

The body Ill and the shell I9 are so formed and disposed with relation to each other as to provide an intervening space 21 connecting the passage I'I with the outer end of all of the gun bores I8. This space 2l, in the embodiment of the invention disclosed, consists of a helical channel in the outer face of the body I0, such channel 21 communicating at its upper end with the passage I'I and'having intermediate portions thereof connecting the outer ends of the gun bores I 8, the

lower end of the channel 21 ending at and communicating with the lowermost of the gun bores Prior to the placing of the shell I9 on 'the body I0 each of the gun bores I8 is loaded as shown in Fig. 2. In the inner end of the bore I8 I place Y a, propelling charge 30, such propelling charge 30 occupying a space which may be referred to as the propelling charge space or chamber 3I communicating with the inner end of the gun bore I8. A projectile 32 is then placed in the gun bore I8 so that it will occupy a position between the propelling charge 30 and the outer end of the bore I8. The shell I9 is then placed on the body I0 in the manner shown in Fig. 1, this shell I9 then sealing the outer ends of the gun bores I8. When the gun is to be lowered into a well, a firing charge of powder 33 is then placed in the firing charge chamber I 6, and the cable connection II is installed. The ring means I4 may consist of any of the known types of electrically ignited fuses. I have shown the ring means I4 as consisting of an electrically fired cartridge 35 disposed in a block 36 which is threaded into the lower end of the body I5 of the cable connection II, the block 36 -holding the cartridge 35 in such position that it will operatively engage the electrical contact 31 which is connected to the conductor I3 of the cable I2.

When the gun is lowered into the well by means of the cable l2 and enters the iluid content of the well, the `hydrostatic pressure of the well is prevented from acting upon the projectiles to force the same rearwardly so as to compress the propelling charges 30; therefore, the propelling charges 3i) are maintained at relatively low pressure. These propelling charges 30 are placed in the spaces 3I at atmospheric pressure. and, during the lowering of the gun into the well, the only increase in pressure against the propelling charges 30 is that which may result frox'n increase in temperature encountered in the well uid. The propelling charge 30 comprises powder grains which may be of any form and are generally either iiat or annular. They are so disposed with relation to each other that the mass of powder of the propelling charge 30 is of cellular structure, that is to say, adjacent substantially each and every one of the grains there is a small gas space. Also, there may be a gas filled space externally of the mass of powder grains.-

Firing of the gun is accomplished by electrically igniting the priming cartridge 35 which in turn ignites the firing charge 33. The combustion products from the burning of the firing charge 33 pass through the passage I1 and then through the space or channel 21 to the outer ends of the gun bores I8, the pressure of these combustion products driving the projectiles rearward so as Y helical channel 21 in the gun body lo, this channel 2l traversing the outer ends of the gun bores I8. The upper end of the fuse 40 may be extended through the passage I1 into the firing charge chamber 33 where it will be ignited by the primer 35. In the outer ends of the gun barrels, as indicated in Fig. 3, a `firing charge 42 is placed, which is ignited by the fuse 40, the pressure generated by the ignition of the charge E2 driving the projectile 32 rearwardly to compress the contents of the propelling charge chamber, to ignite the same in the manner hereinbefore described.

As shown in Fig. 4, a ring charge 44 may be placed in the outer end of eachbore I8 for ignition by a iiame which passes through the channel 21 from the firing charge chamber IE when a heat and/or flame producing charge of powder is burned in the chamber lli. The :force exerted against the projectiles 32 by the burning of the ,iiring charge ed will drive the projectiles 32 rearwardly to compress the contents of the propelling charge chambers 3l, thereby igniting the propelling charges 3U therein.

As explained' hereinbefore, the discharged projectiles penetrate the shell I9 and then they pass through the casing into the formation. When the gun, after its use, is withdrawn from thewell, the gun bores or barrels i8 are reloaded and a new shell i9, consisting simply of a length of steel tubing, is substituted for the perforated shell 19.v

I claim as my invention: l. In a perforating gun of the character described, wherein a propelling charge is red by .drivingthe projectile rearwardly so as to compress the propelling charge, the combination of: a gun body having a. plurality of gun bores leading thereinto from the face thereof, there being a propelling charge chamber communicating with .the rear end of each bore; a, shell around said body in sealed relation thereto, said-body and said shell being so relatively formed as to provide a space'between them communicating with the outer ends of all of said bores; a propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of said `propelling charge chambers; and means for ccmmu'nicating a pressure through said space into the outer ends of said bores to drive said projecdrive said projectiles rearwardly'whereby the l the rear end of each bore; a shell aroundlsaid body in sealed relation thereto, said body and said shell being so relatievly formed as to provide a space between them communicating with the outer ends of all of said bores; a propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardlyso as to compress the contents of said propelling charge chambers; and means for communicating an explosive blast -through said space into the outer ends of said bores to contentsof said propelling charge chambers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell.

3. In a perforating gun of the character described, wherein a propelling charge is red by driving the projectile rearwardly so as to compress the propelling charge, the combination of: a gun body having a plurality of gun bores leadingthereinto from the face thereof, there being 'a propelling charge chamber communicating with the rear end of each bore; a shell around said body'in sealed relation thereto, said body and said shell being so relatively formed as to provide` a space between them communicating with the outer ends of all of said bores; a propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of said propelling charge chambers; a ring charge in the outer end of each bore; and means for transmitting a firing effect through said space to said firing charges thereby exploding said tiring charges so as' to drive said projectiles rearwardly, whereby the contents of said propelling charges will be compressed and said propelling charges ignited to discharge said projectiles from said bores and 'through said shell.

4. In a perforatingvv gun of the characterdescribed, wherein a propelling charge is tired by driving the projectile rearwardly so as to compress the propelling charge, the combination of: a gun body having a plurality of gun bores leading thereinto from the face thereof, there being a propelling charge chamber communicating with the rear end of each bore; a shell around said body in sealed relation thcreto,said body and said shell said bores adapted to be driven rearwardly so as to compress the contents of said propelling charge chambers; a, firing charge -in the outer end of each of said bores; and-means for transmitting an ignition eiect through said space to ignite said ring charges and thereby build up pressure in the outer ends of said bores to drive said projectiles rearwardly, whereby the contents of said propelling charge chambers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell.

of all of said bores, said body and said coverA member being so relatively formed as to provide a space communicating with the outer ends of said bores; a propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of saidprpelling charge Chambers; and means for communicating a pressure through said space into the outer ends of said bores to drive said projectiles rearwardly, whereby the contents of said propelling charge cham- -bers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell.

6. In a perforating gun of the character descri-bed, wherein a propelling charge is fired by driving the projectile rearwardly so as to compress the propelling charge, the 4combination of a gun body having a plurality of gun bores leading thereinto from the face thereof, there being a propelling charge chamber communicating with the rear end of each bore; a thin walled cover member on sai-d body covering the outer ends of al1 of said bores, said body and said cover member being so relatively formed as to provide a space communicating with the outer ends of said bores; a propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of said propelling charge chambers; and means for communicating an explosive blast through said space into the outer ends of said bores to drive said projectiles rearwardly, whereby the contents of said propelling charge chambers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell.

'7. In a perforating gun of the character described, Wherein a propelling charge is red by driving the projectile rearwardly so as 'to compress the propelling charge,` the combination of a gun body having a plurality of gun bores leading thereinto from the face thereof, there being a. propelling charge chamber communicating with the rear end of each bore; Ia shell around said body, said body and said shell being so relatively formed as to provide a space between them communicating with the outer ends of all of said bores; sealing means between the upper and lower ends of said body and said shell, whereby theinterior of said shell will be protected against hydrostatic well pressure; a propelling chargve in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of said propelling charge chambers; and means for communicating an explosive blast through said space into the outer ends of said bores to drive said projectiles rearwardly, whereby the contents of said propelling charge chambers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell.

8. In a perforating gun of the character described, wherein a propelling charge is red by driving the projectile rearwardly so as to compress the propelling charge, the combination of: a gun body having a plurality of gun bores leading thereinto from the face thereof, there being a propelling charge chamber communicating with the rear en-d of each bore; a shell around said body, said body and said shell being so relatively formed lng means between the upper and lower ends of said body and said shell, whereby the interior of said shell will be protected against hydrostatic well pressure; a. propelling charge in each of said propelling charge chambers; projectiles in said bores adapted to be driven rearwardly so as to compress the contents of said propelling charge chambers; and means for communicating an explosive blast through said space into the outer ends of said bores to drive said projectiles rearwardly, whereby the contents of said propelling charge chambers will be compressed and said propelling charges ignited to discharge said projectiles from said bores and through said shell, said last named means comprising walls forming a ring charge chamber communicating 4 with said space, a firing charge in said firing charge chamber, and means for exploding said firing charge.

9. The method of firing a perforating gun structure having a gun body with loaded gun bores, a sleeve on said gun body to cover said bores, and a space within said sleeve communicating with said bores, comprising the steps of producing a pres'sure in the gun structure,rand conducting said pressure through said space to said gun bores to cause ring of the loads therein.

10. The method of ring a perforating gun structure having a gun body with loaded gun bores, a sleeve on said gun body to cover said bores and seal the same against external pressure, and a channel communicating with all of said bores,

- comprising the steps of producing a, pressure in as to provide a space between them communicating with the outer ends of all of said bores; sealthe gun structure, and conducting said pressure through said channel to said gun bores to cause firing of the loads therein.

11. A perforating gun comprising a gun body having loaded gun bores, a sleeve on said body to cover the outer ends of said bores and seal the same against external pressure, means operable to produce a. pressure, means for conducting said pressure to said gun bores, and means acting in response to said pressure to fire said loads.

12. In a perforating gun of the character described, the combination of a gun body having a plurality of gun bores opening at their outer ends in the face thereof; a shell surrounding said body in sealed relation thereto; projectiles in said bores having associated pressure activated charges for propelling them from said bores; and

means for subjecting said charges to an activat- -ing pressure, including achannel interconnecting the outer ends of said bores, one side of said channel being formed by the body and the other side thereof being formed by the shell.

PHILIP W. MARTIN.

REFERENCES CITED The following `references are of record inthe file of this patent:

UNITED STATES PATENTS Number 

